This invention relates to hydraulic pumping of oil wells, and more particularly to a method of installing a pump in existing production tubing so that well fluid can be hydraulically pumped up the existing tubing without requiring removal of the tubing and replacement with another production tubing having a bottom hole assembly.
In the production of offshore oil wells, for example, production tubing extends from an offshore platform down to the well site. Well fluid can flow up the tubing under reservoir pressure until the well quits flowing naturally, after which hydraulic pumping or a gas lift can be used to continue production from the well. A common practice in hydraulically pumping well fluid from an offshore well is to pull the production tubing and install a new string with a bottom hole assembly at the bottom of the new string. A pump installed on the bottom hole assembly continues production by pumping well fluid from the well up the new string. The pump can be installed by conventional wire line equipment, or the pump can be a free pump which is pumped down the new string and coupled to the bottom hole assembly above the well. When production is finished, the free pump can be uncoupled from the bottom hole assembly and pumped to the surface.
Use of a bottom hole assembly is costly, especially when considering the expense of pulling the existing tubing and installing a new string with a bottom hole assembly.
A gas lift also can be used to continue production of well fluid after the well stops flowing by natural reservoir pressure. However, a gas lift can be expensive because of the need for compressors, natural gas supplies, and added equipment.
The present invention provides a method for hydraulically pumping well fluid from a well after the well stops flowing naturally, without requiring the production tubing to be pulled and without requiring use of a bottom hole assembly or a gas lift.